Methods of forming recessed access devices associated with semiconductor constructions

ABSTRACT

The invention includes methods of forming recessed access devices. A substrate is provided to have recessed access device trenches therein. A pair of the recessed access device trenches are adjacent one another. Electrically conductive material is formed within the recessed access device trenches, and source/drain regions are formed proximate the electrically conductive material. The electrically conductive material and source/drain regions together are incorporated into a pair of adjacent recessed access devices. After the recessed access device trenches are formed within the substrate, an isolation region trench is formed between the adjacent recessed access devices and filled with electrically insulative material to form a trenched isolation region.

TECHNICAL FIELD

This invention pertains to methods of forming recessed access devicesassociated with semiconductor constructions.

BACKGROUND OF THE INVENTION

A semiconductor transistor device is a device comprising a gate whichinterconnects a pair of source/drain regions with one another through achannel controlled by the gate. Transistor devices are common circuitdevices of semiconductor constructions. For instance transistor devicescan be incorporated into memory structures, including, for example,dynamic random access memory (DRAM) and static random access memory(SRAM).

A continuing goal in semiconductor fabrication is to increase a level ofintegration, and thus decrease the amount of semiconductor real-estateconsumed by devices. Decreasing the size of transistor devices, however,leads to numerous difficulties. For instance, as the channel-length of atransistor device is decreased, numerous problems occur in attempting tocontrol electron flow between source/drain regions on opposing sides ofthe channel. These problems are generically referred to as short-channeleffects.

One approach that may have utility for overcoming short-channel problemsis to recess transistor devices within a substrate so that the devicesconsume less real-estate than if they were non-recessed, and yet haverelatively long channels. A non-recessed transistor device is shown inFIG. 1, and a recessed device is shown in FIG. 2 for comparison to thenon-recessed device.

Referring initially to FIG. 1, a semiconductor construction 10 isillustrated to comprise a substrate 12. The substrate 12 can comprise,for example, monocrystalline silicon lightly-doped with backgroundp-type dopant. To aid in interpretation of the claims that follow, theterms “semiconductive substrate” and “semiconductor substrate” aredefined to mean any construction comprising semiconductive material,including, but not limited to, bulk semiconductive materials such as asemiconductive wafer (either alone or in assemblies comprising othermaterials thereon), and semiconductive material layers (either alone orin assemblies comprising other materials). The term “substrate” refersto any supporting structure, including, but not limited to, thesemiconductive substrates described above.

A transistor device 14 is supported by the substrate. The transistordevice includes a gate 16 spaced from substrate 12 by a dielectricmaterial 18; includes sidewall spacers 24 along sidewalls of the gate;includes a pair of source/drain regions 20 on opposing sides of thegate; and includes a channel region 22 between the source/drain regions.

The gate 16 can comprise various electrically conductive materials,including, for example, various metals, metal compositions, and/orconductively-doped silicon or other conductively-doped semiconductormaterial. Dielectric material 18 can comprise any suitable material orcombination of materials, and typically will comprise, consistessentially of, or consist of silicon dioxide. Sidewall spacers 24 cancomprise any suitable compositions or combination of compositions, andtypically will comprise one or both of silicon nitride and silicondioxide. Source/drain regions 20 can comprise conductively-doped regionswithin monocrystalline substrate 12, and can comprise heavily-dopedregions with lightly-doped extensions. For instance, the source/drainregions 20 can comprise either heavily n-type doped regions or heavilyp-type doped regions, and can comprise lightly-doped portions extendingunder sidewalls 24. Channel region 22 is doped with a threshold voltageimplant, and operably interconnects the source/drain regions 20 with oneanother when sufficient current passes through gate 16.

FIG. 2 shows a construction 30 comprising a semiconductor substrate 32and a transistor 34 supported by the substrate. The transistor comprisesa gate 36 extending within the substrate, a dielectric material 38between the gate and the substrate, source/drain regions 40 within thesubstrate proximate the gate, and a channel region 42 extending around alowermost portion of the gate and interconnecting the source/drainregions 40 with one another. Although not shown, sidewall spacers can beprovided proximate gate 36 similar to the spacers 24 discussed abovewith reference to FIG. 1.

The substrate 32, dielectric material 38, gate 36 and source/drainregions 40 can-comprise identical materials to those discussed aboveregarding the substrate 12, gate 16, dielectric material 18 andsource/drain regions 20 of FIG. 1. Also, a threshold voltage implant canbe provided within channel region 42 similar to the threshold voltageimplant provided within region 22 of FIG. 1.

A difference between the recessed device construction of FIG. 2 relativeto the non-recessed device construction of FIG. 1 is that the channelregion 42 of the device of FIG. 2 is lengthened by virtue of the channelregion extending around a recessed portion of the gate 36. Such canreduce short-channel effects for the transistor device 34 of FIG. 2relative to the device 14 of FIG. 1.

Although recessed access devices have advantages relative tonon-recessed devices in terms of the packing density that can beachieved while avoiding short-channel effects, there are variousproblems encountered in large-scale fabrication of recessed accessdevices which are to be addressed if recessed access devices are tobecome commercially feasible. Accordingly, it is desired to develop newmethodology for large-scale fabrication of recessed access devices. Oneapplication for recessed access devices is in memory arrays, such as,for example, DRAM arrays. Accordingly, it would be further desirable ifmethodologies developed for large-scale fabrication of recessed accessdevices were applicable to fabrication of memory arrays.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a method of forming recessedaccess devices. A semiconductor substrate is provided. Recessed accessdevice trenches are formed within the substrate. A pair of the recessedaccess device trenches are adjacent one another. Electrically conductivegate material is formed within the recessed access device trenches.Source/drain regions are formed proximate the conductive gate material.The conductive gate material and source/drain regions together form anadjacent pair of recessed access devices (specifically, a pair ofrecessed access transistors). After the recessed access device trenchesare formed within the substrate, an isolation region trench is formedbetween the adjacent recessed access devices. The isolation regiontrench is filled with electrically insulative material to form atrenched isolation region.

In one aspect, the invention includes another method of forming recessedaccess devices. A semiconductor construction is provided, and recessedaccess device trenches are formed within the substrate. The recessedaccess device trenches are filled with a first electrically insulativematerial. The first electrically insulative material is patterned into amask defining a plurality of access device regions. The access deviceregions are islands surrounded by isolation regions. The access deviceregions comprise only portions of the recessed access device trenches.The substrate is etched within the isolation regions to recess thesubstrate of the isolation regions. The recessed substrate is coveredwith a second electrically insulative material to cover the isolationregions. At least a majority of the first electrically insulativematerial is removed while leaving at least a majority of the secondelectrically insulative material. Subsequently, gate material is formedwithin the portions of the recessed access device trenches comprised bythe access device regions.

In one aspect, the invention includes yet another method of formingrecessed access devices. A semiconductor substrate is provided, and afirst patterned mask is formed over the substrate. The first patternedmask has openings extending therethrough defining first locations fortrenches of recessed access devices. The substrate is etched in thefirst locations to form recessed access device trenches extending intothe substrate. The recessed access device trenches are filled with agate material. A first electrically insulative material is formed overthe first patterned mask and over the gate material. The firstelectrically insulative material is patterned into a mask defining aplurality of access device regions. The access device regions areislands surrounded by isolation regions. The access device regionscomprise only portions of the recessed access device trenches. Thesubstrate is etched to recess the substrate of said isolation regions.The recessed substrate is covered with a second electrically insulativematerial. The first electrically insulative material is removed.Subsequently, a plurality of conductive lines are formed. Individualconductive lines extend across multiple access device regions andelectrically interconnect gate material of the multiple access deviceregions with one another.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment illustrating a prior art transistor device.

FIG. 2 is a diagrammatic, cross-sectional view of a semiconductor waferfragment illustrating another prior art transistor device.

FIGS. 3 and 4 are a diagrammatic top view and diagrammaticcross-sectional side view of a semiconductor wafer fragment illustratedat a preliminary processing stage of an exemplary aspect of the presentinvention. The cross-section of FIG. 4 is along the line 4-4 of FIG. 3.

FIGS. 5 and 6 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 3 and 4. Thecross-section of FIG. 6 is along the line 6-6 of FIG. 5.

FIGS. 7 and 8 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 5 and 6. Thecross-section of FIG. 8 is along the line 8-8 of FIG. 7.

FIGS. 9 and 10 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 7 and 8. Thecross-section of FIG. 10 is along the line 10-10 of FIG. 9.

FIGS. 11 and 12 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 9 and 10. Thecross-section of FIG. 12 is along the line 12-12 of FIG. 11.

FIGS. 13 and 14 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 11 and 12. Thecross-section of FIG. 14 is along the line 14-14 of FIG. 13.

FIGS. 15 and 16 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 13 and 14. Thecross-section of FIG. 16 is along the line 16-16 of FIG. 15.

FIGS. 17 and 18 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 15 and 16. Thecross-section of FIG. 18 is along the line 18-18 of FIG. 17.

FIGS. 19 and 20 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 17 and 18. Thecross-section of FIG. 20 is along the line 20-20 of FIG. 19.

FIGS. 21 and 22 illustrate the fragments of FIGS. 3 and 4, respectively,at a processing stage subsequent to that of FIGS. 19 and 20. Thecross-section of FIG. 22 is along the line 22-22 of FIG. 21.

FIGS. 23 and 24 are a diagrammatic top view and diagrammaticcross-sectional side view of a semiconductor wafer fragment shown at apreliminary processing stage of an exemplary aspect of a secondembodiment of the present invention. The cross-section of FIG. 24 isalong the line 24-24 of FIG. 23.

FIGS. 25 and 26 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 23 and24. The cross-sectional view of FIG. 26 is along the line 26-26 of FIG.25.

FIGS. 27 and 28 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 25 and26. The cross-section of FIG. 28 is along the line 28-28 of FIG. 27.

FIGS. 29 and 30 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 27 and28. The cross-section of FIG. 30 is along the line 30-30 of FIG. 29.

FIGS. 31 and 32 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 29 and30. The cross-section of FIG. 32 is along the line 32-32 of FIG. 31.

FIGS. 33 and 34 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 31 and32. The cross-section of FIG. 34 is along the line 34-34 of FIG. 33.

FIGS. 35 and 36 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 33 and34. The cross-section of FIG. 36 is along the line 36-36 of FIG. 35.

FIGS. 37 and 38 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 35 and36. The cross-section of FIG. 38 is along the line 38-38 of FIG. 37.

FIGS. 39 and 40 illustrate the fragments of FIGS. 23 and 24,respectively, at a processing stage subsequent to that of FIGS. 37 and38. The cross-section of FIG. 40 is along the line 40-40 of FIG. 39.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The invention includes various methods for forming recessed accessdevices associated with semiconductor constructions. In particularaspects, structures are formed which contain recessed access devices andshallow trench isolation regions to electrically separate adjacentdevices. Accordingly, recessed access device gate trenches and shallowtrench isolation region trenches are fabricated. In contrast to priorart processes which form shallow trench isolation region trenches priorto formation of recessed access device gate trenches, some methods ofthe present invention form recessed access device gate trenches prior toforming shallow trench isolation region trenches. Although the recessedaccess device gate trenches are formed prior to the shallow trenchisolation region trenches, gate material can be formed within therecessed access device gate trenches either prior to, or after,formation of the shallow trench isolation region trenches.

Exemplary aspects of the invention are described with reference to FIGS.3-40, with FIGS. 3-22 pertaining to a first embodiment aspect of theinvention, and FIGS. 23-40 pertaining to a second embodiment aspect ofthe invention.

Referring initially to FIGS. 3 and 4, a semiconductor construction 100is illustrated at a preliminary processing stage of the first embodimentaspect of the present invention. Construction 100 comprises a substrate102 which can, for example, comprise, consist essentially of, or consistof monocrystalline silicon lightly background-doped with p-type dopant.

A patterned mask 104 is formed over the substrate. The shown patternedmask comprises a first layer 106 comprising, consisting essentially of,or consisting of silicon dioxide; and a second layer 108 comprising,consisting essentially of, or consisting of silicon nitride. The mask104 can be formed into the shown pattern by providing aphotolithographically patterned photoresist (not shown) over mask 104,transferring a pattern from the photoresist to the materials of mask104, and subsequently removing the photoresist.

The patterned mask 104 has openings 110 extending therethrough, withsuch openings defining locations for trenches of recessed accessdevices. The locations of openings 110 can be referred to as firstlocations in the discussion that follows.

Substrate 102 is etched through the first locations defined by mask 104to form recessed access device trenches extending into substrate 102. Inparticular aspects, such trenches will extend into monocrystallinesilicon of substrate. 102. The trenches are shown having bottomperipheries 111 and a depth “D” from an uppermost surface of substrate102 to the bottom peripheries. Such depth can be, for example, fromabout 100 Å to about 2000 Å.

In exemplary aspects of the invention, the substrate 102 can comprisemonocrystalline silicon having p-well and/or n-well implants therein atthe processing stage of FIGS. 3 and 4. The layer 106 can be formed byoxidizing an uppermost surface of the monocrystalline silicon to formthe layer 106 to consist essentially of, or consist of silicon dioxide,and to have a thickness of from about 50 Å to about 100 Å. The nitridecap 108 can comprise a thickness of from about 200 Å to about 500 Å, andtypically will comprise a thickness of from about 300 Å to about 500 Å.

In some aspects (not shown) a critical dimension of the openings 110 canbe shrunk with a two-step process. First, the masking layer 104 isetched to form the shown openings 110. Subsequently, nitride spacers areformed along sidewalls of the openings 110 by providing a siliconnitride layer extending along the sidewalls and within the openings, andsubsequently subjecting such layer to anisotropic etching to form thespacers. The openings can then be extended into substrate 102 afterforming such spacers, so that the openings have a smaller criticaldimension than the dimension initially formed with photolithographicprocessing.

Referring next to FIGS. 5 and 6, mask 104 (FIGS. 3 and 4) is removed anda layer 112 is formed over substrate 102 and within trenches 110. Thelayer 112 can, for example, comprise, consist essentially of, or consistof silicon dioxide. In such aspects, layer 112 can be formed bythermally oxidizing an exposed upper surface of a monocrystallinesubstrate 102.

Referring next to FIGS. 7 and 8, a layer 114 comprising, consistingessentially of, or consisting of silicon nitride is formed over layer112. It is to be understood that the compositions of layers 112 and 114provided herein are exemplary compositions, and that the layers cancomprise any suitable compositions. Layers 112 and 114 can together bereferred to as a first insulative material provided to fill trenches110. The trenches 110 are shown in dashed-line view in FIG. 7 toindicate the locations of the trenches beneath insulative material 114.

Referring next to FIGS. 9 and 10, photolithographically patternedphotoresist 116 is provided over the layer 114. The photoresist definesa pattern which is to be transferred into the first insulative materialcomprising layers 112 and 114. Subsequently, such pattern is transferredto layers 112 and 114 with a suitable etch, which patterns layers 112and 114 into a mask. The mask defines a plurality of access deviceregions 120, 122, 124 and 126. The access device regions are islandssurrounded by an isolation region 130. The access device regions 120,122, 124 and 126 comprise only portions of the recessed access devicetrenches 110 that had been initially formed (i.e., the trenches of FIGS.7 and 8), with remaining portions of the trenches being within isolationregion 130.

The shown access device regions 120, 122, 124 and 126 are substantiallyelliptical in the view of FIG. 9. The substantially elliptical accessdevice regions have primary longitudinal elliptical axes, with anexemplary primary longitudinal elliptical axis being shown as an axis121 within region 120. It is noted that the trenches 110 can beconsidered to comprise primary length axes extending along theirlengths, with an exemplary length axis being illustrated as an axis 123in FIG. 9. In the application illustrated in FIG. 9, the primarylongitudinal elliptical axis 121 is canted relative to axis 123, andaccordingly is not substantially orthogonal to the primary length axis123. It is to be understood, however, that the invention alsoencompasses aspects (such as, for example, an aspect described withreference to FIGS. 31 and 32 below) in which the primary longitudinalelliptical axis of an access device region is substantially orthogonalto the primary length axis of a recessed access device trench.

Referring next to FIGS. 11 and 12, the substrate of isolation regions130 is recessed with an etch. The etch removes portions of trenches 110between recessed access device regions 120, 122, 124 and 126.

After the etch, the recessed substrate of isolation region 130 is at adepth “E” beneath an uppermost surface of substrate 102. In particularaspects, the substrate can be recessed to a level beneath a lowestmostlevel of recessed access device trenches 110 such that depth “E” is atleast about two-fold greater than the depth “D” of FIG. 4. Depth “E” cancorrespond to a depth of a shallow trench isolation region, and inparticular aspects can be from about 500 Å to about 3500 Å.

Two of the trenches 110 of FIG. 12 can be considered to be adjacent toone another, and the isolation region 130 can be considered to be formedbetween such adjacent trenches. For instance, one of the adjacenttrenches can be a trench labeled 131, and the other can be a trenchlabeled 133, and such trenches can be considered to be on opposing sidesof a deep trench formed between them in isolation region 130. In theshown processing of the present invention, the adjacent recessed accessdevice trenches 131 and 133 have been formed prior to formation of thedeep trench between them.

Referring next to FIGS. 13 and 14, photoresist 116 (FIGS. 11 and 12) isremoved, and subsequently an electrically insulative material 136 isformed over the recessed substrate of isolation region 130, as well asover layer 114 of the access device regions 120, 122, 124 and 126. Theaccess device regions 120, 122, 124 and 126 are shown in dashed-lineview in FIG. 13 to indicate the locations of such regions, but it is tobe understood that the regions are beneath insulative material 136 atthe processing stage of FIG. 13.

Material 136 can comprise any suitable composition or combination ofcompositions. In particular aspects, material 136 can correspond to aso-called shallow trench stack, and accordingly can comprise a thinlayer of silicon dioxide along substrate 102, a thin silicon nitrideliner over the silicon dioxide, and a thick silicon dioxide fill withinthe liner. In other words, insulative material 136 can primarilycomprise silicon dioxide, with the bulk silicon dioxide of the materialbeing separated from substrate 102 by a thin silicon nitride liner and athin silicon dioxide liner. The bulk insulative composition of material136 can, in some aspects, be a spin-on-dielectric.

In the view of FIG. 14, the dielectric-filled deep region 130 can beconsidered to comprise a trenched isolation region provided betweenrecessed access device trenches 131 and 133.

Referring next to FIGS. 15 and 16, material 136 is subjected toplanarization (such as, for example, chemical-mechanical planarization)to remove the material from over the layer 114, and to form a planarizedupper surface 137 extending across material 136 and layer 114. Theplanarization of FIGS. 15 and 16 can be considered to remove insulativematerial 136 from over layer 114, while leaving the insulative material136 over the recessed substrate of isolation region 130.

Referring next to FIGS. 17 and 18, layers 112 and 114 are removed fromover substrate 102, while leaving the electrically insulative material136. In some aspects, layers 112 and 114 can be together considered tocomprise a first electrically insulative material, and it can beconsidered that at least the majority of such first electricallyinsulative material is removed while leaving at least a majority of asecond electrically insulative material corresponding to the material136. In the shown aspect, an entirety of the first electricallyinsulative material corresponding to layers 112 and 114 has beenremoved, but it is to be understood that the invention encompasses otheraspects in which less than an entirety of such material is removed. Forinstance, if material 112 comprises silicon dioxide, the material 112can be left to correspond to a gate oxide in subsequent processing.However, it can be advantageous if material 112 is removed, regardlessof whether material 112 comprises silicon dioxide or not, in that suchcan allow a surface of substrate 102 to be cleaned prior to formation ofthe actual gate dielectric material. Accordingly, the material of layers112 and 114 will typically correspond to sacrificial materials.

Dopant can be provided within substrate 102 at the processing stage ofFIGS. 17 and 18 if it is desired to form dopant wells, such as, forexample, p-wells or n-wells.

Referring next to FIGS. 19 and 20, gate dielectric material 140 isformed within recessed access device trenches 110, and subsequentlyconductive gate material 142 is formed over the gate dielectric materialand within the trenches to fill the trenches. In the shown aspect of theinvention, conductive gate material 142 comprises a first layer 144 anda second layer 146. The layers 144 and 146 join at an interface 147.Layer 144 can, for example, comprise, consist essentially of, or consistof conductively-doped silicon; and layer 146 can, for example, comprise,consist essentially of, or consist of one or more metal-containingcompositions. The metal-containing compositions can be pure metal and/ormetal-containing compounds. In particular aspects, layer 146 cancomprise a stack of tungsten/tungsten silicide/titanium nitride, indescending order in the view of FIG. 20.

The shown gate material 142 not only fills the trenches 110, but alsoextends outside of such trenches. Further, the interface between themetal-containing compositions of layer 146 and the conductively-dopedsilicon of layer 144 (i.e., the interface 147) is outside of thetrenches.

An electrically insulative cap 150 is formed over conductive gatematerial 142. Cap 150 can comprise any suitable composition orcombination of compositions, and in particular aspects will comprise,consist essentially of, or consist of one or both silicon dioxide andsilicon nitride.

The access device regions 120, 122, 124 and 126 are shown in dashed-lineview in FIG. 19 to indicate that the regions are beneath insulative cap150.

Referring next to FIGS. 21 and 22, materials 140, 144, 146 and 150 arepatterned into conductive lines extending across access device regions120, 122, 124 and 126. More specifically, the materials 140, 144, 146and 150 are patterned into a plurality of lines 160, 162, 164 and 166,with each of the lines extending across multiple access device regionsand electrically connecting gates associated with different accessdevice regions with one another.

Source/drain regions 170, 172, 174, 176, 178 and 180 are formed withinsubstrate 102 and proximate the electrically conductive gate material144. The source/drain regions can be doped to any suitable dopant type,and can comprise any suitable dopants. The source/drain regions can beformed by implanting dopant into substrate 102 to an appropriate depth.The conductive gate material and source/drain regions together form aplurality of transistor devices 180, 182, 184 and 186 supported bysubstrate 102. Such transistor devices correspond to recessed accessdevices having gates extending within the recessed access devicetrenches 110.

Each of transistor devices 180, 182, 184 and 186 can be considered tocomprise a gate electrically connecting a pair of source/drain regionswith one another. For instance, transistor device 180 can be consideredto comprise a gate electrically connecting source/drain regions 170 and172 with one another; device 182 can be considered to comprise a gateelectrically connecting source/drain regions 172 and 174 with oneanother; device 184 can be considered to comprise a gate electricallyconnecting source/drain regions 176 and 178 with one another; and device186 can be considered to comprise a gate connecting source/drain regions178 and 180 with one another.

The transistor devices can be incorporated into a dynamic random accessmemory (DRAM) array by connecting some of the paired source/drainregions to bitline contacts and others to storage node contacts (i.e. tocapacitor storage nodes). In the shown aspect of the invention,source/drain regions 170, 174, 176 and 180 are connected to capacitorstorage nodes 190, 192, 194 and 196, respectively; and source/drainregions 172 and 178 are connected to bitlines 198 and 200, respectively.Thus, the shown construction can be incorporated into a DRAM array.

Referring next to FIGS. 23 and 24, such illustrate a semiconductorconstruction 300 at a preliminary processing stage of a secondembodiment aspect of the present invention. In referring to the drawingsassociated with the second aspect embodiment of the invention, similarnumbering will be used as was used above in describing the first aspectembodiment of the invention, where appropriate.

Construction 300 comprises the substrate 102, patterned mask 104 oflayers 106 and 108, and trenches 110 described previously with referenceto FIGS. 3 and 4, and thus corresponds identically to the constructiondiscussed above with reference to FIGS. 3 and 4.

Referring next to FIGS. 25 and 26, gate dielectric material 302 isformed to line the bottom of trenches 110, and subsequently gatematerial 304 is formed within the trenches and over the dielectricmaterial 302.

Dielectric material 302 can, for example, comprise, consist essentiallyof, or consist of silicon dioxide. In such aspect, material 302 can bedeposited, or can be formed by oxidizing exposed silicon from substrate102 within trenches 110. Dielectric material 302 can be formed in twosteps, if so desired, with one of the steps being to initially form afirst silicon dioxide material within trenches 110, and the other stepbeing to strip the first dielectric material from within the trench andform another dielectric material within the trench which can be a betterquality silicon dioxide dielectric than that initially provided.

Gate material 304 can comprise, consist essentially of, or consist ofsilicon. The silicon can be conductively-doped as-deposited, or can bedeposited in an non-conductively-doped form and subsequently doped withan appropriate implant at a later processing stage.

The construction of FIG. 26 is shown to comprise a planarized uppersurface 305 extending across gate material 304 and across insulativematerial 108. Such can be formed by initially providing gate material304 to cover material 108 as well as to fill the trenches, andsubsequently subjecting material 304 to planarization (such as, forexample, chemical-mechanical polishing), to remove material 304 fromover material 108 and form the planarized upper surface 305.

An enhancement implant and/or threshold voltage implant can be providedwithin substrate 102 prior to formation of gate material 304 withintrenches 110, if desired.

Although gate material 304 is shown having a planarized surfacecoextensive with an uppermost surface of layer 108, it is to beunderstood that the gate material can also have a surface recessed belowthe elevational level of the uppermost surface of layer 108. In someaspects, it can be preferred that silicon-containing material 304 berecessed below the uppermost surface of layer 108.

Referring next to FIGS. 27 and 28, uppermost surfaces of material 304and layer 108 are subjected to oxidation to form an oxide 310 over layer108, and an oxide 312 over layer 304. In particular aspects of theinvention, layer 108 will comprise, consist essentially of, or consistof silicon nitride, and accordingly oxide 310 will comprise, consistessentially of, or consist of silicon oxynitride; and layer 304 willcomprise, consist essentially of, or consist of silicon, and accordinglyoxide 312 will comprise, consist essentially of, or consist of silicondioxide. The oxides 310 and 312 can be formed to be from about 30 Åthick to about 60 Å thick.

Referring next to FIGS. 29 and 30, an electrically insulative material314 is provided over oxides 310 and 312. Material 314 can, for example,comprise, consist essentially of, or consist of silicon nitride, and canbe deposited to a thickness of from about 300 Å to about 500 Å. In someaspects of the invention, the compositions of 310, 312 and 314 can betogether considered to form an insulative material 316 provided over thefirst patterned mask 104 and gate material 304.

Trenches 110 are shown in dashed-line view in FIG. 29 to indicate thelocations of the trenches.

Referring next to FIGS. 31 and 32, material 316 is patterned into a maskdefining a plurality of access device regions 320, 324, 326, 328, 330,332, 334 and 336; and defining an isolation region 340 surrounding theaccess device regions. Patterning of material 316 can be accomplished byproviding a photolithographically patterned photoresist mask (not shown)over material 316, transferring a pattern from the photoresist mask tomaterial 316, and subsequently removing the photoresist mask.

After material 316 is patterned, substrate 102 is etched withinisolation region 340 to recess the substrate of such isolation region.The recessed substrate of the isolation region is at an elevationallevel below the lowestmost elevational level of trenches 110, and insome aspects is at least two-fold deeper than the elevational level oftrenches 110.

The etching within isolation region 340 removes gate material 304 fromwithin the isolation region, while leaving the gate material within theaccess device regions 320, 324, 326, 328, 330, 332, 334 and 336. Theetching within isolation region 340 can be accomplished with, forexample, a reactive ion etch.

An oxide 342 and a nitride liner 344 are provided within the etchedisolation region 340, and in the shown aspect also extend over material314. Oxide 342 can, for example, comprise, consist essentially of, orconsist of silicon dioxide along substrate 102; and nitride 344 can, forexample, comprise, consist essentially of, or consist of siliconnitride. The oxide can be formed by oxidation of exposed materials ofconstruction 300, and accordingly can comprise a different compositionalong substrate 102 than along materials 108 and 314; or alternativelycan be formed by deposition. Oxidation can be preferred, in that suchcan repair plasma-induced damages that may have occurred during thereactive ion etch, and can also encroach into gate-dielectric atinterfacial surfaces to provide low leakage between gate polysilicon andthe bulk silicon of substrate 102. The oxide is preferably formed to athickness of from about 30 Å to about 80 Å. The nitride liner 344 can bedeposited over the oxide layer 342, and ultimately can function as aprotective layer for a subsequent spin-on glass deposition process.

It is noted that the access device regions of FIG. 31 are shown to beelliptical similar to the access device regions of FIG. 9. However,unlike the access device regions of FIG. 9, the access device regions ofFIG. 31 have primarily longitudinal elliptical axes which aresubstantially orthogonal to primary length axes of recessed accessdevice trenches 110.

Referring next to FIGS. 33 and 34, dielectric material 350 is providedto fill recessed isolation region 340. Dielectric material 350 can be aspin-on glass. Dielectric material 350 can initially be formed to coverinsulative material 316, as well as to fill recessed isolation region340, and subsequently planarization (such as, for example,chemical-mechanical polishing) can be utilized to remove the dielectricmaterial from over insulative material 316 and form the shown planarizedsurface 351 extending over dielectric material 350 and layer 314. Insome aspects, insulative material 316 (comprising materials 314, 310 and312) can be referred to as a first insulative material, and insulativematerial 350 can be referred to as a second insulative material.

Referring next to FIGS. 35 and 36, layer 314 (FIG. 34) is removed. Suchcan be accomplished with a wet oxide etch to slightly recess the spin-onglass below the nitride of material 314, followed with a wet nitridestrip to remove material 314. The wet nitride strip can selectively stopat the oxide materials 310 and 312.

Referring next to FIGS. 37 and 38, a plurality of lines 370, 372, 374and 376 are formed to extend across access device regions 320, 324, 326,328, 330, 332, 334 and 336. The lines comprise a conductive material 380and an insulative cap 382. Conductive material 380 can comprise, forexample, a stack of titanium nitride/tungsten silicide/tungsten (inascending order in the view of FIG. 38), and cap 382 comprise, consistessentially of, or consist of silicon nitride.

The lines can be formed by initially depositing suitable materials oflayers 380 and 382 entirely across the uppermost surface of construction300, and subsequently patterning the materials by: formingphotolithographically patterned photoresist over the layers 380 and 382,transferring a pattern from the photoresist to the underlying layers 380and 382, and subsequently removing the photoresist.

The construction of FIGS. 37 and 38 can be incorporated into a DRAMarray similarly to the construction of FIGS. 21 and 22. Specifically,appropriate conductively-doped diffusion regions can be formed proximatetransistor gates comprised by conductive gate material 144, andcapacitor constructions and bitline constructions can be electricallycoupled with the source/drain regions.

FIGS. 39 and 40 illustrate an alternative aspect relative to that ofFIGS. 37 and 38. Specifically, construction 300 can be subjected toplanarization prior to formation of lines 370, 372, 374 and 376. Suchplanarization removes layer 108 (FIGS. 35 and 36), and forms the shownplanarized surface 390. Planarized surface 390 is shown on material 106,but it is to be understood that the planarization can also extendthrough material 106. If the planarization extends through material 106,another dielectric material can be formed over substrate 102 in place ofthe material 106 prior to formation of the lines. The construction ofFIG. 40 can be incorporated into a memory array in a manner similar tothat discussed above regarding the construction of FIG. 39.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming recessed access devices associated with asemiconductor construction, comprising: providing a semiconductorsubstrate; forming recessed access device trenches within the substrate;filling the recessed access device trenches with a first electricallyinsulative material; patterning the first electrically insulativematerial into a mask defining a plurality of access device regions, theaccess device regions being islands surrounded by an isolation region;the access device regions comprising only portions of the recessedaccess device trenches; etching into the substrate of said isolationregion to recess the substrate of said isolation region; covering therecessed substrate with a second electrically insulative material tocover the isolation region with the second electrically insulativematerial; removing at least the majority of the first electricallyinsulative material while leaving at least the majority of the secondelectrically insulative material; and after removing at least themajority of the first electrically insulative material, forming gatematerial within the portions of the recessed access device trenchescomprised by the access device regions.
 2. The method of claim 1 whereinthe substrate comprises monocrystalline silicon, and wherein therecessed access device trenches extend into the monocrystalline siliconof the substrate.
 3. The method of claim 1 wherein the firstelectrically insulative material comprises a silicon-nitride-containinglayer over a silicon-dioxide-containing layer.
 4. The method of claim 3wherein the removing at least the majority of the first electricallyinsulative material removes both the silicon-nitride-containing layerand the silicon-dioxide-containing layer.
 5. The method of claim 1wherein the access device regions are substantially elliptical; whereinthe substantially elliptical access device regions have primarylongitudinal elliptical axes; wherein the recessed access devicetrenches have primary length axes; and wherein the primary longitudinalelliptical axes of the substantially elliptical access device regionsare substantially orthogonal to the primary length axes of the recessedaccess device trenches.
 6. The method of claim 1 wherein the accessdevice regions are substantially elliptical; wherein the substantiallyelliptical access device regions have primary longitudinal ellipticalaxes; wherein the recessed access device trenches have primary lengthaxes; and wherein the primary longitudinal elliptical axes of thesubstantially elliptical access device regions are not substantiallyorthogonal to the primary length axes of the recessed access devicetrenches.
 7. The method of claim 1 wherein the covering the recessedsubstrate with a second electrically insulative material is accomplishedby: forming the second electrically insulative material over the firstelectrically insulative material and over the recessed substrate of theisolation region; and planarizing the second electrically insulativematerial to remove the second electrically insulative material from overthe first electrically insulative material while leaving the secondelectrically insulative material over the recessed substrate of theisolation region.
 8. The method of claim 1 wherein the forming the gatematerial includes: forming the gate material within said portions of therecessed access device trenches and over the second electricallyinsulative material; and patterning the gate material to form lines ofthe gate material; individual lines extending across multiple of theaccess device regions.
 9. The method of claim 8 further comprisingforming the gate material as part of a stack of silicon,metal-containing material, and insulative capping material; and whereinthe patterning simultaneously patterns the silicon, metal-containingmaterial, and insulative capping material.
 10. The method of claim 8further comprising forming source/drain regions associated with gatematerial of the recessed device regions, the gate material comprisinggates which electrically interconnect pairs of source/drain regions withone another; at least some of the paired source/drain regions comprisinga bitline contact and a storage node contact and being incorporated intoDRAM devices.
 11. A method of forming recessed access devices associatedwith a semiconductor construction, comprising: providing a semiconductorsubstrate; forming a first patterned mask over the substrate, the firstpatterned mask having openings extending therethrough defining firstlocations for trenches of recessed access devices; etching the substratethrough said first locations to form recessed access device trenchesextending into the substrate; filling the recessed access devicetrenches with a gate material; forming a first electrically insulativematerial over the first patterned mask and over the gate material;patterning the first electrically insulative material into a maskdefining a plurality of access device regions, the access device regionsbeing islands surrounded by an isolation region; the access deviceregions comprising only portions of the recessed access device trenches;etching into the substrate of said isolation region to recess thesubstrate of said isolation region, the etching also removing the gatematerial from between the access device regions while leaving the gatematerial within the access device regions; covering the recessedsubstrate with a second electrically insulative material to cover theisolation region with the second electrically insulative material;removing the first electrically insulative material; and after removingthe first electrically insulative material, forming a plurality ofconductive lines, individual conductive lines extending across multipleaccess device regions and electrically interconnecting gate material ofthe multiple access device regions with one another.
 12. The method ofclaim 11 wherein the first patterned mask comprises asilicon-nitride-containing layer over a silicon-dioxide-containinglayer.
 13. The method of claim 11 wherein the filling the recessedaccess device trenches with gate material comprises: forming the gatematerial to cover the first patterned mask and to be within thetrenches; and planarizing the gate material to remove the gate materialfrom over the first patterned mask while leaving the gate materialwithin the recessed access device trenches.
 14. The method of claim 13wherein the gate material comprises silicon and is conductively-dopedprior to the planarizing.
 15. The method of claim 13 wherein the gatematerial comprises silicon and is not conductively-doped prior to theplanarizing.
 16. The method of claim 13 wherein the first insulativematerial comprises oxide and silicon nitride; wherein the planarizingforms a planarized surface extending across the first patterned mask andthe gate material, and wherein the forming the first electricallyinsulative material comprises: oxidizing the planarized surface to formthe oxide of the first insulative material extending across the firstpatterned mask and the gate material; and forming the silicon nitride ofthe first insulative material over the oxide of the first insulativematerial.
 17. The method of claim 16 wherein the planarized surfacecomprises silicon nitride along the first patterned mask and comprisesconductively-doped silicon along the gate material; and wherein theoxide comprises silicon oxynitride over the first patterned mask andcomprises silicon dioxide over the gate material.
 18. The method ofclaim 11 wherein: the substrate comprises monocrystalline silicon; theetching into the first locations to form the recessed access devicetrenches etches into the monocrystalline silicon to a first depth; andthe etching into the substrate of said isolation region etches into themonocrystalline of the substrate to a second depth that is at leasttwo-fold greater than the first depth.
 19. The method of claim 11wherein the forming the second electrically insulative materialcomprises: forming the second electrically insulative material to coverthe first electrically insulative material and recessed substrate; andplanarizing the second electrically insulative material to remove thesecond electrically insulative material from over the first electricallyinsulative while leaving the second electrically insulative material tocover the recessed substrate of the isolation region.
 20. The method ofclaim 11 further comprising removing at least substantially all of thefirst electrically insulative material prior to forming the conductivelines.